In recent years there has been a steadily increasing need for security for one's property and person. The instance of burglaries and forced entries into homes, office buildings, schools, industrial areas and other structures has steadily increased. One approach to this problem has been through the development of a multitude of alarm or warning systems, but law enforcement authorities constantly point to the need for the use of more secure locks and lock mechanisms.
One type of lock mechanism which is regarded highly by law enforcement officials is the so-called "dead bolt." This type of lock has the advantage of requiring a key to open the same from inside as well as the outside of the structure. Thus, if the door is provided with a dead bolt, a burglar cannot enter through a small opening and open a door from the inside to carry away large objects. One of the primary disadvantages, however, of a dead bolt lock mechanism is that it is somewhat difficult and costly to install. The average homeowner often is not willing to attempt to install a dead bolt and is further unwilling to pay the added cost for installation by a locksmith. Still further, a dead bolt is difficult to adapt for use in securing sliding glass doors of the type found in many modern homes.
Attempts have been made to utilize the relatively simple and inexpensive padlock as part of a locked latch or bolt mechanism. These approaches have ranged from the relatively simple systems, such as is disclosed in U.S. Pat. No. 1,376,697, which may also include padlocking together of members as shown in U.S. Pat. Nos. 1,201,940 and Re.22,918, to the relatively complex use of built-in latches or multiple padlocks, bolts and keeper bars, as shown in U.S. Pat. Nos. 3,012,430 and 3,094,861. Such simple systems are often unsuitable for use by the home owner, while the complex systems are difficult to install and require modification of the door structure, in addition to excessive expense.
In addition to dead bolts or security locks, a number of seal-type locks have been developed in which the primary objects is to detect breaking and entry, not to prevent the same. Thus, U.S. Pat. Nos. Re. 15,937, 1,004,831, 1,020,721, 1,096,759 and 995,232 are all examples of seal-type locks in which entry will require destruction of a seal, but the lock assemblies are constructed in a manner in which either the bolt assembly or the latch assembly can be relatively easily forced open or removed from the structures on which they are mounted.